Re: Patch: Write Amplification Reduction Method (WARM)

On Tue, Mar 21, 2017 at 1:08 PM, Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> On Tue, Mar 21, 2017 at 10:04 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> I think that's a good question. I previously expressed similar
>> concerns. On the one hand, it's hard to ignore the fact that, in the
>> cases where this wins, it already buys us a lot of performance
>> improvement. On the other hand, as you say (and as I said), it eats
>> up a lot of bits, and that limits what we can do in the future. On
>> the one hand, there is a saying that a bird in the hand is worth two
>> in the bush. On the other hand, there is also a saying that one
>> should not paint oneself into the corner.
>
> Are we really saying that there can be no incompatible change to the
> on-disk representation for the rest of eternity? I can see why that's
> something to avoid indefinitely, but I wouldn't like to rule it out.

Well, I don't want to rule it out either, but if we do a release to
which you can't pg_upgrade, it's going to be really painful for a lot
of users. Many users can't realistically upgrade using pg_dump, ever.
So they'll be stuck on the release before the one that breaks
compatibility for a very long time.

--
Robert Haas
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